01 -
Set your oven to 175°C and hit your 20 x 20 cm pan with a swipe of nonstick spray.
02 -
Toss flour with powdered sugar in a big bowl. Rub in that cold butter with your hands, a fork, or pastry cutter till you get a chunky crumb. Layer it into the greased pan and push down all over with your hands.
03 -
Bake that crust about 15 minutes—stop once it’s firm but still pale. Pull it out and let it sit a sec.
04 -
Blend sugar, flour, cornstarch, and salt in another bowl. Pour in the eggs and rhubarb pieces. Only stir enough to mix—it’s okay if it’s still a little lumpy.
05 -
Spread that rhubarb custard over your hot base. Slide the pan back into the oven. Bake roughly 38–45 minutes—it should look set and not jiggle when you gently rock it.
06 -
Let it chill out at room temp. Pop in the fridge a few hours so it gets solid, then slice into bars nice and clean.